Lights out detector for providing a continuous indication of the failure of lamps which are illuminated intermittently or have intermittent failures

ABSTRACT

A circuit for indicating failure of a vehicle brake light includes a phototransistor adjacent to the brake light which controls the conduction of a first transistor so that upon failure of the brake light, the first transistor is biased into conduction. The output of the first transistor controls a latching circuit which includes a second transistor in series with an indicating lamp and the vehicle battery. The latching circuit also includes a phototransistor in parallel with the first transistor and positioned adjacent to the indicating lamp. Upon failure of the brake light, the first transistor is biased into conduction to bias the second transistor into conduction and energize the indicator lamp. The phototransistor senses the illumination of the indicator lamp and maintains the second transistor biased into conduction irrespective of the condition of the brake light or the brake switch.

United States Patent Barnum Aug. 29, 1972 Assignee: General Motors Detroit, Mich.

Filed: Oct. 27, 1970 Appl. No: 84,311

Inventor:

Corporation,

US. Cl ..340/251, 250/213 A, 315/82, 340/80 Int. Cl. ..G08b 21/00 Field of Search ..340/251, 80; 315/129, 134, 315/82, 83; 250/213 A, 213 R References Cited UNITED STATES PATENTS 8/1969 Vasel ..315/134 9/1960 Ghandhi ..250/213 A 2/ 1962 Bowerman, Jr ..250/213 A 8/1961 Vize ..250/213 A l/l969 Kawai et al ..315/83 Primary Examiner-John W. Caldwell Assistant Examiner-Marshall M. Curtis Attorney-Jean L. Carpenter and Paul Fitzpatrick [57] ABSTRACT A circuit for indicating failure of a vehicle brake light includes a phototransistor adjacent to the brake light which controls the conduction of a first transistor so that upon failure of the brake light, the first transistor is biased into conduction. The output of the first transistor controls a latching circuit which includes a second transistor in series with an indicating lamp and the vehicle battery. The latching circuit also includes a phototransistor in parallel with the first transistor and positioned adjacent to the indicating lamp. Upon failure of the brake light, the first transistor is biased into conduction to bias the second transistor into conduction and energize the indicator lamp. The phototransistor senses the illumination of the indicator lamp and maintains the second transistor biased into conduction irrespective of the condition of the brake light or the brake switch.

6 Claims, 1 Drawing Figure -lull! I W zbil gD LIGHTS OUT DETECTOR FOR PROVIDING A CONTINUOUS INDICATION OF TIE FAILURE OF LAMES WHICH ARE ILLU it ATED TNTE ENTLY OR HAVE INTE E FAILURES This invention relates to a lamp failure indicator and more specifically, to a lamp failure indicator for continuously providing an indication of the failure of a lamp which has an intermittent failure or a lamp which is intermittently operated.

Lamp failure indicators which provide an indication of the failure of a lamp during the time period in which the lamp has failed or is operated are known. When this form of indicator is utilized in conjunction with a lamp which is intermittently energized, or when the lamp being monitored has an intermittent failure due to a ENT v faulty lamp, the resulting signal is a short term signal. It

sometimes may be desirable to provide a continuous indication during and subsequent to an intermittent failure instead of the aforementioned short term signal.

It is therefore the general object of this invention to provide a lamp failure indicator which continuously provides an indication upon the failure of a lamp which is intermittently operated or which has an intermittent failure.

It is another object of this invention to provide a lamp failure indicator having an indicating lamp for indicating the failure of a lamp being monitored which includes a latching circuit having a light sensor which monitors the output of the indicating lamp to latch the indicating lamp in an energized condition to continuously indicate the occurrence of a lamp failure.

These and other objects of this invention are accomplished by providing a phototransistor for monitoring the illumination of the lamp being operated. This phototransistor controls the conduction of a transistor which energizes an indicating lamp when the phototransistor senses a lamp failure. Upon the occurrence of the lamp failure, a second phototransistor senses the illumination of the indicating lamp to permanently bias the transistor into conduction to maintain the indicating lamp illuminated.

The invention may be best understood by reference to the following description of a preferred embodiment and the FIGURE which is a schematic diagram of the preferred embodiment of this invention.

The preferred embodiment of this invention is hereinafter described with reference to a vehicle brake light and is described with reference thereto for illustration purposes only. As will be understood by one skilled in the art, the lamp failure indicator described may be utilized in other applications such as, for example, vehicle turn signal systems, head lamp systems or any other system having lamps which are intermittently operated or having lamps which may have intermittent failures.

Referring to the figure, a vehicle brake light is connected to ground, and to the positive terminal of the vehicle battery 12 through a normally open brake switch 14 which is closed by the vehicle operator while braking the vehicle. As can be seen, the voltage of the battery 12 is applied to the brake lamp 10 when the brake switch 14 is closed by the vehicle operator.

A resistor 16 and a phototransistor 18 are connected in series with the brake switch 14 and in parallel with the vehicle brake lamp 10, the emitter electrode of the positioned relative to the brake lamp 10 so as to be illuminated thereby.

The collector electrode of the phototransistor 18 is connected to the base electrode of a transistor 20 whose emitter electrode is connected to ground and whose collector electrode is connected to the base electrode of a transistor 22 through a resistor 24. A phototransistor 26 having characteristics similar to the phototransistor 18 is connected in parallel with the transistor 20 such that the collector and emitter electrodes of the phototransistor 26 are connected respectively to the collector and emitter electrodes of the transistor 20. An indicating lamp 28 is connected between the collector electrode of the transistor 22 and ground and is positioned within the vehicle so as to be easily observed by the vehicle operator. The emitter electrode of the transistor 22 is connected to one terminal of a vehicle ignition switch 30 whose other terminal is connected to the positive terminal of the vehicle battery 12. The parallel combination of a capacitor 32-and a resistor 34 is connected between the emitter and base electrodes of the transistor 22. The phototransistor 26 is positioned relative to the indicating lamp 28 so as to be illuminated thereby when current is supplied to the indicating lamp 28.

The operation of the lamp failure indicator will now be described. With the ignition switch 30 closed and the brake switch 14 open, no current is supplied to the base electrode of the transistor 20 through the resistor 16, with the result that the transistor 20 is biased into nonconduction. Consequently, the transistor 22 is nonconducting and the indicating lamp 28 is not illuminated. The phototransistor 26, which is biased into conduction when illuminated by the indicating lamp 28, is therefore nonconductive.

When the brake switch 14 is closed, voltage from the vehicle battery 12 is supplied to the phototransistor 18 and the base of the transistor 20 through the resistor 16. If the brake lamp 10 is operative, it will illuminate the phototransistor 18, which becomesv conductive. Therefore, the transistor 20 is biased into nonconduction to cause the indicating lamp 28 to remain extinguished as previously described. lf, when the brake switch 14 is closed, the brake lamp 10 has failed, the phototransistor 18 will remain nonconductive. Therefore, the current supplied to the base of the transistor 20 through the resistor 16 causes the transistor 20 to conduct, which in turn biases the transistor 22 into conduction to illuminate the indicating lamp 28. Upon the illumination of the indicating lamp 28, the phototransistor 26 conducts to latch the transistor 22 in a conducting state. Subsequently, regardless of the actuation of the brake switch 14 or the illumination or nonillumination of the brake lamp 10, the indicating lamp 28 will remain illuminated to provide a continuous indication of the failure of the lamp 10 until the ignition switch 30 is opened to deenergize the indicating lamp 28 and thereby deenergize the latching circuit.

Since the brake lamp does not provide illumination during its warm-up period, during which period the transistor is biased into conduction, the transistor 22 is prevented from being biased into conduction for a time period determined by the capacitor 32 and the resistors 24 and 34. This time period prevents the indicating lamp 128 from being illuminated initially to allow the brake lamp 10 to become illuminated if it has not failed.

As can be seen, a number of sets of phototransistors l8 and transistors 20 may be connected in parallel so as to monitor a number of lamps. Therefore, the indicating lamp 28 will be illuminated upon the failure of any one of the plurality of lamps being monitored.

As previously indicated, the lamp 10 may take the form of a vehicle turn signal lamp or any other lamp. 1f the lamp 10 is a lamp which is continuously illuminated, it can be seen that if the lamp 10 intermittently fails, the indicating lamp 28 will be turned on to give a continuous indication of the intermittent failure.

Although this invention has been described as relating to a preferred embodiment, the invention should not be deemed limited thereto, since other embodiments and modifications will readily occur to one skilled in the art.

I claim:

1. An indicator for indicating the failure of a first lamp comprising first light sensing means responsive to the failure of the first lamp for generating a lamp failure signal; a second lamp; second light sensing means responsive to the energization of the second lamp for generating a latching signal; and switch means responsive to the lamp failure signal and the latching signal for energizing the second lamp, whereby the second lamp is energized by the switch means upon the occurrence of a lamp failure signal and maintained energized thereafter by the latching signal generated by the second light sensing means in response to the energization of the second lamp to provide a continuous indication of a failure of the first lamp irrespective of the condition of the first lamp subsequent to the failure.

2. An indicator for indicating the failure of a first lamp comprising a voltage source; switch means for supplying voltage from the voltage source to the first lamp, the first lamp being illuminated thereby in the absence of a failure and being nonilluminated thereby upon the occurrence of a failure; first light sensing means responsive to the simultaneous occurrence of voltage being supplied from the voltage source to the first lamp by the switch means and the nonillumination of the first lamp for supplying a lamp failure signal; a second lamp, the second lamp being illuminated in response to the energization thereof; means responsive to the lamp failure signal for energizing the second lamp; and second light sensing means responsive to the illumination of the second lamp for maintaining the second lamp energized irrespective of the switch means and the first lamp, whereby the second lamp is continuously energized upon the failure of the first lamp to provide a continuous indication of the failure.

3. An indicator for providing a continuous indication of the failure of a first lamp which is illuminated intermittently comprising first light sensing means positioned relative to the first lamp for sensing the: illumination thereof; means for intermittently supplying voltage simultaneously to the first lamp and the first light sensing means for intermittently illuminating the first lamp, the first light sensing means being responsive to the failure of the first lamp to be illuminated while voltage is being supplied thereto for generating a lamp failure signal; a series circuit including a power source, switch means having a conducting state when energized and a second lamp, the second lamp being illuminated by the power source when the switch means is energized; means for supplying the lamp failure signal to the switch means, the switch means being energized thereby to illuminate the second lamp; and second light sensing means positioned relative to the second lamp and responsive to the illumination thereof for energizing the switch means, whereby the switch means is maintained in an energized condition and the second lamp is maintained illuminated upon the failure of the first lamp to provide a continuous indication of the failure.

4. An indicator for providing a continuous indication of the failure of a first lamp which is illuminated intermittently comprising first light sensing means positioned relative to the first lamp for sensing the illumination thereof; means for intermittently supplying voltage simultaneously to the first lamp and the first light sensing means for intermittently illuminating thefirst lamp, the first lamp having a warm-up period between the time when voltage is supplied thereto and the illumination thereof, the first light sensing means being responsive to the failure of the first lamp to be illuminated while voltage is being supplied thereto for generating a lamp failure signal; a series circuit including a power source, switch means having a conducting state when energized and a second lamp, the second lamp being illuminated by the power source when the switch means is energized; time delay means responsive to the lamp failure signal for energizing the switch means when the duration of the lamp failure signal exceeds the warm-up period of the first lamp; and second light sensing means positioned relative to the second lamp and responsive to the illumination thereof for energizing the switch means, whereby the switch means is energized and the second lamp is illuminated when the duration of the lamp failure signal exceeds the warm-up period of the first lamp to provide a continuous indication of the failure of the first lamp.

5. A latching circuit for maintaining a circuit in an energized condition when initially momentarily energized comprising a series circuit including a power source, switch means having a conducting state when energized and a lamp, the lamp being illuminated by the power source when the switch means is energized; means for momentarily energizing the switch means; and light sensing means responsive to the illumination of the lamp for energizing the switch means whereby the switch means is maintained in an energized condition and the lamp is maintained illuminated when the switch means is momentarily energized.

6. A latching circuit for maintaining a circuit in an energized condition when initially momentarily energized comprising a series circuit including a power source, a transistor and a lamp, the lamp being illuminated by the power source when the transistor is biased into conduction; means for momentarily biasing the transistor into conduction; and light sensing means responsive to the illumination of the lamp for biasing the transistor into conduction, whereby the transistor is maintained biased into conduction and the lamp is maintained illuminated when the transistor is momentarily biased into conduction. 5 

1. An indicator for indicating the failure of a first lamp comprising first light sensing means responsive to the failure of the first lamp for generating a lamp failure signal; a second lamp; second light sensing means responsive to the energization of the second lamp for generating a latching signal; and switch means responsive to the lamp failure signal and the latching signal for energizing the second lamp, whereby the second lamp is energized by the switch means upon the occurrence of a lamp failure signal and maintained energized thereafter by the latching signal generated by the second light sensing means in response to the energization of the second lamp to provide a continuous indication of a failure of the first lamp irrespective of the condition of the first lamp subsequent to the failure.
 2. An indicator for indicating the failure of a first lamp comprising a voltage source; switch means for supplying voltage from the voltage source to the first lamp, the first lamp being illuminated thereby in the absence of a failure and being nonilluminated thereby upon the occurrence of a failure; first light sensing means responsive to the simultaneous occurrence of voltage being supplied from the voltage source to the first lamp by the switch means and the nonillumination of the first lamp for supplying a lamp failure signal; a second lamp, the second lamp being illuminated in response to the energization thereof; means responsive to the lamp failure signal for energizing the second lamp; and second light sensing means responsive to the illumination of the second lamp for maintaining the second lamp energized irrespective of the switch means and the first lamp, whereby the second lamp is continuously energized upon the failure of the first lamp to provide a continuous indication of the failure.
 3. An indicator for providing a continuous indication of the failure of a first lamp which is illuminated intermittently comprising first light sensing means positioned relative to the first lamp for sensing the illumination thereof; means for intermittently supplying voltage simultaneously to the first lamp and the first light sensing means for intermittently illuminating the first lamp, the first light sensing means being responsive to the failure of the first lamp to be illuminated while voltage is being supplied thereto for generating a lamp failure signal; a series circuit including a power source, switch means having a conducting state when energized and a second lamp, the second lamp being illuminated by the power source wHen the switch means is energized; means for supplying the lamp failure signal to the switch means, the switch means being energized thereby to illuminate the second lamp; and second light sensing means positioned relative to the second lamp and responsive to the illumination thereof for energizing the switch means, whereby the switch means is maintained in an energized condition and the second lamp is maintained illuminated upon the failure of the first lamp to provide a continuous indication of the failure.
 4. An indicator for providing a continuous indication of the failure of a first lamp which is illuminated intermittently comprising first light sensing means positioned relative to the first lamp for sensing the illumination thereof; means for intermittently supplying voltage simultaneously to the first lamp and the first light sensing means for intermittently illuminating the first lamp, the first lamp having a warm-up period between the time when voltage is supplied thereto and the illumination thereof, the first light sensing means being responsive to the failure of the first lamp to be illuminated while voltage is being supplied thereto for generating a lamp failure signal; a series circuit including a power source, switch means having a conducting state when energized and a second lamp, the second lamp being illuminated by the power source when the switch means is energized; time delay means responsive to the lamp failure signal for energizing the switch means when the duration of the lamp failure signal exceeds the warm-up period of the first lamp; and second light sensing means positioned relative to the second lamp and responsive to the illumination thereof for energizing the switch means, whereby the switch means is energized and the second lamp is illuminated when the duration of the lamp failure signal exceeds the warm-up period of the first lamp to provide a continuous indication of the failure of the first lamp.
 5. A latching circuit for maintaining a circuit in an energized condition when initially momentarily energized comprising a series circuit including a power source, switch means having a conducting state when energized and a lamp, the lamp being illuminated by the power source when the switch means is energized; means for momentarily energizing the switch means; and light sensing means responsive to the illumination of the lamp for energizing the switch means whereby the switch means is maintained in an energized condition and the lamp is maintained illuminated when the switch means is momentarily energized.
 6. A latching circuit for maintaining a circuit in an energized condition when initially momentarily energized comprising a series circuit including a power source, a transistor and a lamp, the lamp being illuminated by the power source when the transistor is biased into conduction; means for momentarily biasing the transistor into conduction; and light sensing means responsive to the illumination of the lamp for biasing the transistor into conduction, whereby the transistor is maintained biased into conduction and the lamp is maintained illuminated when the transistor is momentarily biased into conduction. 